Process for cracking of hydrocarbon oils



Oct. 2, 1934.

U. S. JENKINS PROCESS FOR ORAOKING OF HYDROOARBON OILS Filed June 9. 1930 2 Sheets-Sheet l i vw www j M. W A, E W w |lf||N|||I|1| l Q uw wm. fx nu@ 2 Sheets-Sheet 2 Filed June 9, 1930 mux NND.

Patented. Oct. 2, 1934` PaocEss ron cnscxmo or mnocsnnou ons Ulysses S. Jenkins, Chicago, lll., assigner to y Jenkins Petroleum Process Company, Chicago,

lll., a corporation of Wisconsin Application June 9, 1930, Serial No. 459,997

5 Claims. (Cl. 196-49) This invention relates to certain improvements in the process ci cracking hydrocarbon oils, and particularly to a process for cracking petroleum hydrocarbon oils under lcertain synchronously alternating operative conditions.

Known cracking processes generally comprebend the continuous production of gasoline from petroleum hydrocarbon oils of high molecular weight, wherein such hydrocarbon oils are subjected to a cracking temperature under superatmospheric pressure, with operative phases varying from concurrently continuous to irregularly intermittent. The yield of gasoline under such conditions is largely dependent upon the stability ci the ratio maintained between the volume of chargingstock supplied, vapor released and degraded stock withdrawn, with due regard to existing temperature and pressure.

A high gasoline yield is more commonly achieved under concurrently continuous operation, but the otherwise optimum in results is frequently penalized by the diillculty in maintaining a constant withdrawal ratio of partially converted stock, due to agglomerate deposits clogging or partially clogging. the withdrawal line; the introduction oi solid adsorptive material with charging stock being likewise subject to somewhat resemblant disturbing factors.

Similarly, irregularly intermittent charging and withdrawal of partially converted stock, as existing where such phases are controlled 'by the level or temperature of the oil undergoing cracking, militates against the unvarying ratios between operative phases, so essential to the contingous production oi maximum gasoline yield.

It is a primal object of the invention to eliminate the above-mentioned objectionable features, respectively present in so-called concurrently continuous, and irregularly intermittent operation; by adopting a system of synchronous, regularly periodic charging of raw stock and Withdrawal of partially converted base; thereby securing a continuum of operative emciency.

A corollary object of the invention incident to such synchronous operation, is to effect the introduction of a predetermined constant volume of charging stock (and where desired, adsorbent) and the withdrawal of a lesser predetermined constant volume of partially converted stock (and where employed, adsorbent and msociated carbon sforrning substance) under a likewise predetermined periodicity, proportionate to the rate of gasoline formation at the cracking temperature employed.

An important object of the invention is to maintain such predetermined periodicity at a frequency creative of a surge or wave eiiect of sutilcient intensity to purge the charging and withdrawal lines at each recurrent cycle.

Another object of the invention is izo-maintain 50 such xed ratio between the above mentioned predetermined constant volumes, periodicity and rate of gasoline formation as to effect a substantially constant operative oil level.

The invention comprehends a harmonic balance of the reacting liquids, vapors and solid contents of a cracking cycle, productive of a more regular and increased gasoline yield.

Sequential to the preceding, a purpose of the invention is the production of gasoline and partially converted stock of unvarying composition and quantity, productive of minimum expense in subsequent refining.

In order that the invention may be better understood, reference will be made to the accom- Y panying drawings, essentially diagrammatic in nature, where Fig. 1 represents in vertical elevation the application of the invention to a known type of cracking still; and Fig. 2 and Fig. 3 represent in vertical elevation modications of 30 such application.

Referring to Fig. 1. there is disclosed a horizontal, cylindrical drum l.. superimposed over front and rear sluiceways 2 and 3, connected to subjacent cross drums 4 and 5, respectively; the 85 latter being themselves joined together through the medium of the tube bank 6.

The assembly is mounted over a furnace 7, heated by any suitable means 6, preferably gas or fuel oil; positive cyclic circulation of the contents of the system being effected by the propeller 9. mounted on shaft 10, passing through stufling box 11, and driven by motor 12, or other suitable mechanism.

Fromthe drum 1, which is provided with the usual accessories, such as liquid level gauge 13, safety valve 14, pressure gauges and thermometers (not shown), the vapor line 15 serves to conduct the cracked vapor to the reflux tower 16, with reflux therefrom returning to the drum 1 through 100 line 17. The lines 18 and 19 serve as regular, and emergency reject lines respectively, the latter being controlled by the valve 20. Charging of the system is effected by the high pressure pump 21, taking suction from a source not shown, 105 and discharging through line 22, as controlled by pressure regulating valve 23, past check valve 24 to accumulating drum 25. 'I'he latter, which may be of any convenient size suiiicient to hold an excess of charging stock for a predetermined interval, is connected to the reflux tower 16, by the equalizing pressure line 26, which enters the reflux tower 16 to a suilcient depth te allow only relatively heavy vapor to pass into the drum 25 during pressure equalization between such drum and reflux tower, thus preventing return of desirable light gasoline fractions to the system.

The accumulating drum 25 is also connected to the reux tower 16 by the fiow line 27, the latter being of sufficiently greater capacity than the charging line 24, as to permit of a greater flow from the drum 25 than the amount fed thereto, during any given period; the interval of such open flow being regulated by the balanced timing valve 28. Cracked gasoline vapor escapes through the line 29, as controlled by the pressure regulati'ngvalve 31, which may be automatically operated if so desired. Final control of the flow` of reject is eifected by valve 32, with open intermediate ow governed by balanced timing valve 33. The reject passes to the low pressure vaporizer 34, where under a pressure less than maintained in the cracking system, a portion vaporizes, escaping through line 35; and the remainder is eliminated as a liquid residue through line 36.

The balanced timing valves 28 and 33 may be of any of the well known types; such as of the type covered by Letters Patent No. 1,767,637 and No. 1,829,772, issued to Wilhjelm on June 24, 1930, and November 3, 1931, respectively, the electrical timing mechanism being similar to that generally used on intermittently lighted electric signs. It is to. be understood that this invention is not limited to any particular type of timing valve but embraces every type of valve which may be automatically operated at predetermined and regularly recurrent intervals controlled independently of temperature, pressure or level gonditions existing within the cracking apparatus.

In Fig. 2, the drum 25 is shown above the reflux tower 16, to aiord greater hydrostatic head of flow, but it will be understood that the exact location of such drum in respect to such tower is optionaLas well as the location and arrangement of the connecting lines, provided a. regularly interrupted, uniform iiow of charging stock be effected from said drum to said tower.

In Fig. 3, the withdrawal line 18, connects to the reject accumulating drum, or sub-cracking zone 38, which may be of any convenient size suicient to hold an excess of reject for a predetermined interval. The line 39 unites the drum 38 with the low pressure vaporizer 34, with quantity of flow thereto .controlled by the valve 40. Provision is also made for release of a relatively small portion of cracked gasoline vapor from the drum 38, through line 41, as controued by valve 42.

As an operative example of the process, it will be assumed that the system is filled with oil to the level 37, or that the drum 1 is half full, and that such contents are under cracking conditions of heat and pressure, say 780 F. at 135 lbs., with forced cyclic circulation being maintained by the propeller 9.

It will be further assumed that 3,000 bbls. or 126,000 U. S. gallons are charged to the system every 24 hours, so that 337 cu. in. per second (at 60 F.) enter the accumulating drum 25; the apparent gallonage increasing in proportion to the degree of preheat or adsorbent supplied to the charging stock. Any adsorbent employed will be preferably introduced in such a degree of fineness as to remain substantially uniformly suspended vin the drum 25 during the intervals of nondischarge therefrom, although any known type of agitating device, such as a mechanically driven stirrer, or a gas jet may be employed in such drum if desired.

If an operating periodicity be maintained, wherein each 100 second period consists of a 10 second reject interval without feed, and a 90 second feed interval without reject, eiected through the instrumentality of the balanced timing valves 28 and 33, respectively; then there will enter the reflux tower 16, in the first 100 second period, 90 x 337 cu. in., or 30,330 cu. in., while during the next 10 seconds, 10 x 337 cu. in., or 3,370 cu. in. will accumulate in the drum 25. Inasmuch as the line 27 is o1' greater capacity than the charging line 22, in every successive 100 second period there will be delivered into the reux tower 16 the quantity delivered into the drum 25 in 90 seconds, i. e., 30,330 cu. in. plus the 3,370 cu. in. accumulated in the previous 100 second period, or a total of 33,700 cu. in.; which at the operative temperature specified (780 F.), will become 45,800 cu. in. through thermal expansion. It will be understood that the apparent volume actually deliveredl to the system may approach the latter figure, depending on the degree of preheat to which the charging stock is exposed, after its predetermined unit measurement.

During the above considered periodicity, it will be also assumed that 45% of the equivalent volume of charging stock introduced, passes off as cracked vapor through the reiiux tower 16, and that 55% is rejected as a liquid through line 18, which may extend within the drum 4, with such extension provided with a plurality of openings, or such line may be installed at another point of the non-extraneously heated liquid circuit. Line 18 discharges tothe low pressure vaporizer 34, such discharge occurring during the 10 second interval in which the balanced timing valve 33 is full open, and its counterpart valve 28 remains closed. 'I'hese percentages applied to the equivalent of 45,800 cu. in. of charging stock at 780 F. appear appendixed in tabular form, in which it will be noted that the total amount of material withdrawn from the cracking system every 100 seconds equals the amount charged thereto for the same period.

Percent N ame product Cu. in.

45 Cracked vapor 20, 610

55 Liquid reject 25, 190

In other words, with the balanced timing valves 28 and 33, timed to operate at a definite synchronous periodicity, corresponding to a predetermined rate of charging and rejection of partially converted base, proportional to the cracking time factor of the oil under treatment, the operating oil level 37 will remain substantially unchanged, and the benets of synchronous, regularly recurrent charging and withdrawal as described in the objects of the invention, will be secured.

The surge or wave effect of regularly interrupted charging is beneficial in purging the flow line 27, reflux tower 16 and reflux line 17 from introduced adsorbent, while the shock of the regularly periodic release of the relatively large quantity of partially converted base (including adsorbent with associated carbon forming substance) n a small fraction of the time of the normal continuously operative period, is particularly effective in dislodging agglomerates and maintaining open communication through line 18 to the low pressure vaporizer 34; and incidentally the desired continuum of operation.

In the modiilcation 4shown in Fig. 3, the same surge or shock release effective in purging the reject line 18, is obtained under regular periodic discharge of partially converted base, with such ilow passing to the reject accumulating drum or sub-cracking zone 38, while continuous discharge is conjointly effected from such zone to the low pressure vaporizer 34 by proper setting of valve 40; thus affording the advantage of shock release from the active cracking zone, and continuous release from the accumulating drum or subcracking zone 38.

In the cited example, during the second interval of nondischarge, as well as the 10 second interval of flow into the accumulating drum or sub-cracking zone 38, a constant ilow oi' reject lwill occur therefrom under a slightly varying pressure, but of sufficient intensity to prevent substantial vaporization within said zone and permit of the formation at a somewhat reduced rate of conversion of a quantity of gasoline vapor, which may be continuously withdrawn through line dl, as controlled by valve 42, if desired. -On

laccount of the somewhat reduced temperature in the sub-cracking zone 38, there is little tendency for agglomerate deposit to form, and continuity of ow from such. zone to the low pressure vaporizer 3d is easily maintained by proper adjustment of the valve 40, thus affording a continuous production of recycle vapor and the desired continuum of operation.

The invention is not limited to the quantities, temperatures, pressures and periodicities discussed in the illustrative example; nor to the 'particular form oi apparatus disclosed. For instance, the accumulating drum 25 may be` eliminated, and the pump 21, or other suitable apparatus, be provided with a balanced timing valve. arranged to discharge to the reflux tower i6, independent of the pressure therein obtaining, a regularly interrupted constant volume of charging stock under a predetermined periodicity.

Other modifications within the scope of the invention will suggest themselves to those skilled in the art; and what I consider new and desire to protect by Letters Patent is:

l. In an oil cracking process for the production of gasoline and other oils from heavy hydrocarbon oils wherein heavy hydrocarbon oils at a cracking temperature are continuously circulated under pressure from a vapor separating drum through heating tubes and back into said drum to maintain a mass of oil therein from which vapors are evolved, the steps of conducting ofi vapors so evolved, charging additional hydrocarbon oil to be cracked into said drum in an amount surhcient to replace vapors conducted oi and to substantially increase the normal mass of oil in said drum, interrupting such charging of additional hydrocarbon oil at predetermined and regularly recurring intervals established independently of conditions of temperature, pressure or mass of oil in said drum, and during the inter-- -duce a surge effect on said mass of oil whereby carbon in said drum is flushed out in the oil thus withdrawn.

2. In an oil cracking process for the production of gasoline and other oils from heavy hydrocarbon oils wherein heavy hydrocarbon oils at a cracking temperature are continuously circulated under pressure from a vapor separating drum through heating tubes and back into said drum to maintain a mass of oil therein from which vapors are evolved, the steps of conducting off vapors so evolved, and alternately charging additional hydrocarbon oil to be cracked into said drum and withdrawing oil from said drum, these alternate charging and withdrawal steps being eiTected at regularly recurring intervals corresponding to a predetermined time factor for the oil undergoing cracking and being thus effected independently of variations in conditions of temv peratnre, pressure or mass of oil in said drum..

3. In an oil cracking process for the production of gasoline and other oils from heavy hydrocarbon oils wherein heavy hydrocarbon oils at a cracking temperature are continuously circulated under pressure from a vapor separating drum through heating tubes and back into said drum to maintain a mass of oil therein from which vapors are evolved, the steps of conducting off vapors so evolved, and alternately charging additional hydrocarbon oil to be cracked into said drum and withdrawing oil from said drum, these alternate charging and withdrawal steps being effected at predetermined and regularly recurring intervals established independently of conditions of temperature, pressure or mass of oil in said drum, the regularly recurring intervals during which oil is withdrawn being relatively short with respect to the regularly recurring intervals during which oil is charged.

4. In an oil cracking process for the production of gasoline and other oils from heavy hydrocarbon oils wherein heavy hydrocarbon oils at a cracking temperature are continuously circulated under pressure from a vapor separating drum through heating tubes and back into said drum to maintain a mass of oil therein from which vapors are evolved, the steps of conducting oir vapors so evolved, continuously charging additional oil to be cracked into an accumulating drum, discharging oil from said accumulating drum into said vapor separating drum in an i amountvsufiicient to replace vapors conducted oil drum, and during the intervals that suclr discharge of oil from said accumulating drum is interrupted withdrawing oil from said vapor separating drum in an amount sufficient to substantially decrease the normal mass of oil in said drum and at such a rate as to produce a surge effect on said mass of oil whereby carbon in said drum is ilushed out in the oil thus withdrawn.

5. In an oil cracking process for the production of gasoline and other oils from heavy hydrocarbon oils wherein heavy hydrocarbon oils at a cracking temperature are continuously circulated under pressure from a vapor separating drum through heating tubes and back into said drum to maintain a mass of oil therein from which vapors are evolved, the steps of conducting oi vapors so evolved, charging additional hydrocarbon oil to be cracked into said drum in an amount sumcient to replace vapors conducted of! and to substantially increase thenormal mass of oil in said drum, interrupting such charging of additional hydrocarbon oil at predetermined and regularly recurring intervals established independently of conditions of temperature, pressure or mass of oil in said drum, and during the intervals that such charging of oils is interrupted withdrawing oil from said vapor separating drum into a reaction drum in an amount sufiicient to substantially decrease the normal mass of oil in said vapor separating drum and at such a rate as to produce a surge eil'ect on said mass of oil whereby carbon in said vapor separating drum is ilushed out in the oil thus withdrawn to said reaction drum, conducting oil vapors evolved from oil in said reaction drum. and continuously passing the unvaporized oil and carbon from said reaction drum to a zone of reduced pressure to eiIect further vaporization of said oil.

ULYSSES S. JENKINS.

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